Heretofore, adhesives using polychloroprene as a base were mainly of a solvent type. However, in recent years, demand for not employing a solvent has increased in view of problems such as toxicity, possible danger of fire and environmental pollution by an organic solvent during the production or use of solvent type adhesives. As a method for not employing a solvent, a method of substituting a latex adhesive for a solvent type adhesive is considered to be effective, and a study has been actively conducted on latex adhesives using various polymers.
Among them, a chloroprene latex adhesive is coated on both adherends to be bonded, such adhesive layers are dried and then bonded, whereby it exhibits high adhesiveness immediately after the bonding. From such a characteristic, it is expected to be useful as an aqueous contact type adhesive, but on the other hand, it is not necessarily satisfactory in the initial adhesive performance and in the balance of the heat resistance, water resistance, etc. with the adhesive properties, and improvements in this respect have been desired.
For example, JP-B-51-39262 discloses a method for producing a polychloroprene latex adhesive, wherein from 3 to 5 parts by weight of a long chain fatty acid or a rosinate is used as an emulsifier, per 100 parts by weight of chloroprene, and the monomer is polymerized at a temperature lower than 20° C. in an alkaline emulsion in the presence of from 0.09 to 0.15 part by weight of n-dodecyl mercaptan, and polymerization is terminated when the conversion of the monomer reaches from 90 to 98% to obtain a latex of polychloroprene containing from 40 to 90 wt % of a gel content, and a tackifier resin is blended thereto. However, latexes prepared in accordance with Examples of such publication lack in the contact property, and in order to make contact adhesion possible, a large amount of a tackifier resin is required to be added, and it takes time for the development of the strength, and the initial adhesive performance has not been necessarily satisfactory.
The present invention is intended to solve such problems of the prior art and to provide a chloroprene latex composition which is excellent in the initial adhesive performance and which is excellent also in the balance of the heat resistance and the water resistance, a method for its production and an adhesive composition employing it.